1. Field of the Invention
The invention relates in general to transportation apparatus, and more specifically to passenger conveyors such as escalators and moving walks which have a plurality of steps, platforms, or pallets.
2. Description of the Prior Art
In conveyors for transporting people between spaced landings, such as escalators and moving walks of the type which include a plurality of steps, platforms or pallets, treads of the steps, platforms or pallets are conventionally provided with a plurality of longitudinally extending grooves and cleats. The landings at each end of the escalator or moving walk include combplates which have a plurality of teeth which mesh with the cleats. The teeth are inclined upwardly away from the load bearing portion of the transportation apparatus, to facilitate transfer of passengers between the moving conveyor and the landing.
The combplate is understandably the source of many problems since it provides the interface between the moving conveyor and a stationary landing. There must be a clearance between the moving cleats of the treads and the teeth of the combplate, and they must properly mesh in a manner which minimizes the possibility of objects becoming caught or trapped at this interface.
Many U.S. patents have been issued which relate to different arrangements for improving the combplate. For example, U.S. Pat. No. 2,110,547 discloses that the clearance between the combplate platform and the tops of the cleats may be greater than that between the teeth in the bottom of the tread grooves, because of step tilt due to a heavy load on the rear of the step. This patent also states that depending upon the design of the stairway, these clearances may be the same. This patent then discloses a structure for filling in the space between the bottom of the tread grooves and between the combplate platform and the top of the cleats, to resist the pressure of anything which the tread tries to carry along with it underneath the combplate.
U.S. Pat. No. 3,458,025 discloses a protective, resilient structure which completely covers the teeth of the combplate and which includes resilient fingers which lead the conventional metallic teeth of the combplate in meshing with the cleats of the stairway treads.
U.S. Pat. No. 3,687,257 discloses mounting the combteeth on a slider bar which permits self-alignment of the combteeth in the conveyor grooves.
While these patents all disclose structures which improve certain aspects of the combplate, it would be desirable to provide a new and improved combplate structure which will greatly extend its useful operating life. Further, this desirable result should be obtained without adding significantly to the manufacturing cost thereof, without complicating maintenance of the transportation apparatus, and without adversely affecting the functioning of the combplate.
More specifically, it would be desirable to eliminate, or at least greatly reduce, the breakage of combplate teeth. A heavy person, or a sharp descending blow by a person's foot, may apply a load to the combplate adjacent to the teeth which is sufficient to momentarily deflect the teeth downwardly and cause them to contact and to be mechanically stressed by the moving step, platform or pallet. This may result in immediate breakage of a tooth, or it may start a crack which after repeated stressing of the combplate may cause breakage of the tooth. Tooth breakage may occur due to such deflecting loads regardless of the relative dimensions of the teeth and cleats. For example, it is immaterial whether the teeth of the combplate bottom in the cleat grooves before the cleats contact the tooth grooves, or the cleats contact the tooth groove before the teeth bottom in the cleat grooves, or even if both types of contact occur simultaneously.